Science Fair Project Encyclopedia
In some physics textbooks and articles, certain quantities are defined with the opposite sign from that which is used in other publications. This lack of standardization is a frequent source of confusion, misunderstandings, and even outright errors. A standard choice of sign for a definition is called a sign convention. Sometimes, this term is used more broadly to include factors of i and 2π.
A noncomprehensive list of sign conventions:
- In relativity, the metric signature could either be +--- or -+++.
- The choice of in the Dirac equation.
- The sign of the Faraday 2-form in gauge theories.
- The sign of work in the first law of thermodynamics.
- Time dependence of an electromagnetic wave:
- exp( - iωt) (mainly used by physicists)
- exp( + jωt) (mainly used by engineers)
It is often considered good form to state explicitly which sign convention is to be used at the beginning of each book or article.
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